Previously, many types of wire tying tools have been used in endeavoring to provide an effective means for producing an automatic or semi-automatic twist tie of a wire. Prior art is replete with devices that twist tie structural wire for use with joints in concrete reinforcing bar. Others have developed tools for other purposes, such as bag ties and double loop bar ties for binding sacks and bundling elongated items utilizing pre-looped wire. Still others have directed their attention to tying cable harnesses with thermoplastic, resin coated lacing tape.
Concrete reinforcing bar tying tools have been in use utilizing either a pneumatic or an electric energy source. Some use an electric drill motor, and others employ integral motors and electromagnetic solenoids. In most cases, the tool employs jaws that surround the joint and a wire is automatically, or manually, threaded through the jaws to develop the tying sequence.
While the operation of looping, cutting, and twisting wires is all basically similar, those advanced specifically for reinforcement bar must be large and robust, as the wire attachment must have sufficient strength to insure that the reinforcing bars are not displaced while pouring heavy fluid concrete directly over the joint. Dedicated motors and solenoids have also been used in conjunction with lever arms and gears to provide the needed strength and stoutness for this application and, as such, are large and powerful.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however, the following U.S. patents are considered related:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 5,217,049 Forsyth Jun. 8, 1993 4,953,598 McCavey Sep. 4, 1990 4,362,192 Furlong et al Dec. 7, 1982 3,970,117 Zamansky et al Jul. 20, 1976 3,821,058 Miller Jun. 25, 1974 3,590,885 Ward Jul. 6, 1971 ______________________________________
Forsyth, in U.S. Pat. No. 5,217,049, teaches a portable, hand operated power tool that automatically ties intersecting rebar. The device employs an electric drill motor as the rotating power source. The drill motor selectively engages a housed transmission and jaw assembly that encircles the work piece. Wire is stored on a belt mounted reel and fed around guide channels integral with the jaws. Electromagnets control retractable levers preventing rotation, however, when withdrawn the drill motors motion rotates the device to produce a twist tie of the wire.
U.S. Pat. No. 4,953,598 of McCavey discloses a hand held power tool also for rebar connection. The tool includes a body that houses the operating components and provides a wire reel holder, handle with trigger and support for the wire channel guide that momentarily surrounds the rebar joint. The rebar tying wire is fed through the housing with rollers to a circular turret, including two side-by-side clamping jaws which hold one end of the wire. The feed wheels reverse, thereby removing the slack from the wire and tighten the rebar joint. The other end of the wire is clamped and cut, then the entire turret, including the attaching jaws, is rotated to twist the wire ends together after the channel guide is rotated from the joint. Three motors and four electromagnetic solenoids are used to provide the torque and linear force for the device.
Furlong et al U.S. Pat. No. 4,362,192 again, is directed to rebar tying. A fixed and .a movable jaw is Clamped around the rebar joint and a predetermined length of wire is fed into guiding grooves within the jaws forming a loop. The end of the wire is cut to length by a cutter bar on a rotatable mandrel having opposed radial flange sections. Relative rotation of the inner mandrel to an outer mandrel performs the wire cutting and twisting. Controls provide proper positioning of the openings for passage of wire upon each operational cycle. An electric motor and gear reduction arrangement, with a clutch and brake, provide the rotational torque and a series of solenoids open and close the jaws and provide timing sequence functions of rotation.
U.S. Pat. No. 3,970,117 issued to Zamansky et al presents a twister for wire ties that incorporate loops on both ends of a short length of wire. The wire ties are manually placed around the object to be fastened and a hook is inserted into both wire loops. When the handle of the twister is manually pulled away from the wire, the integral D.C. motor is engaged rotating the hook and completing the twisting procedure. When pulling force is released, the motor is disengaged by spring pressure.
Millers U.S. Pat. No. 3,821,058 is directed to fastening a length of thermoplastic, resin coated harness cable lacing tape around a cable bundle by twisting, fusing, and cutting the tape. The hand held tool contains a motor which rotates a tubular drive shaft with a twisting end. The heating and severing function is contained within the jaws retracted into a tool barrel. Lacing tape is supplied through a shaft and is manually looped around the cable bundle with the free end attached to the twisting member. The drive shaft is rotated, which twists the tape and simultaneously the jaws are extended which sever and fuse the tape.
U.S. Pat. No. 3,590,885 of Ward teaches a hand tool for tying rebars with a twist that avoids bunching or piling of the convolutions of the tie on top of one another. Spring loaded plates, that are shiftable, are located on one end of the tool body, which are rearranged by the ends of the wire loop during the twisting operation, such that the entire body moves away from the work piece. The power is provided by pneumatic air pressure.
It may be seen that the prior art incorporates large, heavy mechanisms that employ pneumatic power or electrical drives requiring numerous separate motors, clutches, brakes, and electromagnetic solenoids, etc., to accomplish the task at hand.